Liquid level indicating system



Nov. 16,. 1943. B. WINTON I LIQUID LEVEL INDICATING SYSTEM Filed Sept.30, 1942 IFi/UETZZU 7". Lewm l3. I Vinioz Patented Nov. 16, 1943""asams's' v uoumnnvnnmmommo sYs'r EMt Lewis I B. Wint onQ Greenwich,Conn; I assignor to Application s eptember so, 1942, Serial No.46o,217ACiaims, (o1,'73 -s0'2 f This invention relates to liquid levelindicating devices, particularly for boilers orlike pres' surecontainers, and the object is to providean improved constructionfor'indicating the level of liquid in the containerby means of adifferen' tial hydrostatic manometer wherein the 'eilect of the surgingof the liquid-in the" container due to tipping of the system as a whole,suchas'ocr curs in marine use when the ship rolls or pitches, isefiectually minimized. I I

My invention will be well understood by reierence to the followingdescriptionltaken inconnection with the accompanyingdrawing,where- 1n. J

a vertical section through a boiler drum; and

Fig. 2 is a diagram correspondinggenerally to a horizontal section. i fif Referringto Fig. 1, I have there indicatedvery diagrammatically aliquid container 3", which may be taken as the top drum of a marineboiler,

and a U -tube manometer, herein shown as of the erect U type asdistinguished from an inverted U-tube, having an indicating leg L and acompanion leg L, containinga suitable manometric fluid; which in thecase or the erect U -tube is heavier than Water- The 'leg'L is connectedto the water-containing spaces of the boiler J anid the leg L to a datumchamberE'jin the form offa cup adapted to be replenishedwith liquid andhaving an overflow! whereby'thereis established therein a column ofwater of f xed height at a location atleast as high as the normal highwater level offthe boilerjand corresponding to the line E in Fig; 1;There is thus impressed up- Fig. 1 is a diagram corresponding sheral1ytoa as early as in'the patent to 'I'ripp and Wadleigh 722,645, 'March- 10,1903, and therefhave been later embodiments thereof. In practice thesehave not been found satisfactory, particularly for marine use. Usuallythe datum chamber 5 has been located exteriorly of the boiler at aboutthe location of the ordinary gage glass, the two being commonlyconnected'to th e usual water column. 1 Now, theus'ual gage is afar'fromsatisfactory instrument, particularly on a moving vessel; and many ofthe constructions proposed indeed exaggerated the'errors of agage glass.My study of the prior constructions leads me' to believe that thedesigners did not havean appreciation of *the' problems involved andaccepted as a standard to which their indicators more or lessapproximated theordinary gage glass in spite of its actualrecognizedinability to indicate clearly and accurately the water level. Thus,referring to Fig. 1, suppose that the boiler shown istilted inthe planeof the paper, as" by a rolling or pitching of :the vessel, so that thesurface of the water standing at the level Etherein assumes thepo'sitionE. This may be visualized by actually turning-the drawingcounterclockwise. so that the line E is horizontal.

"Ihcxbody of water inthe boiler surges toward the left-ha'nden'd thereofand in the proportion shown would rise"completely above the topof gageglass G at that end oftheboiler. If the ship then 'rolled 'in'theopposite direction the On the leg L a variable liquidhead correspondingto the actual'level of water in the container and on the leg L aconstant head corresponding to the height of the line E, and thedifference between these heads is a function of the water level in thecontainer and is measured by the manometer. In particular the .surfaceof the manometric liquid in the indicating leg L rises as the level ofthe water rises toward E and that leg at least is made in parttransparent, as by being formed in the manner of a "gage-glass,

to permit 9 eti .thea s el-l he rat o-o travel of the manometricliquidin the leglLtoQthe fluctuations of the liquidlevel the boiler may besuitably determined, taking intoaccountthe specific gravity of themanometricyliquidgby properly proportioning the cross-sectionalareas ofthe manometer legs. V

A construction as above described is notp n itself new; being in itsessence diSclosedfitJfis water would sink to'the bottom of the gageglass, and in the case of a vessel in a seaway there would be aconstantffiuctuation or surging in r the glass. i

" Theoretically, as indicated by the line E, .the level of water wouldbe constant at the center line of the-boiler. Of course, in practice thelevel of the water is affected-by other causes, as, f or exarnple,boils, whereby areas of higher level arise due to steamoomingout of thetubes, butso far 'as bodily-displacement ofthe system "goes, the levelof water at the center line should be as substantially constantas couldbe 'expected V r.

In the case of a U-tube havingspaced legs as herein shown, asimilarsurg'ing effect takes place as the system is inclined.

If the datum chamber 5 werelocated substantially atthe center line ofthe boiler and the .legsl of the u-tub'e, atj leastin"the indicatingportions thereof," concentric or coaxial, as described in my. copendingapplication; Serial'No. ..4.6,0,2l6, filed Sept. 30, 1942 ;we would bemeasguring atheoretically constant height unafiected trasted with theindications of a gage glass or installations of similar inaccuracy.

I will first discuss the matter., i5rom'a theoreti-n cal standpoint andafterwards indicate certain cos 0, the angle of inclination measured atthe center lines, and although the actual heads will vary with theinclination, their relation will be always the same. It will thus beseen that if D and d are properly correlated at the equalizing level sothat there will be no error produced due to surging, the indications ofthe manometer will be proportional to the changes of level in the boilerwithout errors due to surging.

v .If the U-t'ube were of the inverted type with the manometric fluidhaving a specific gravity less than water, the expression (Sp. GSp. W)

"'derived. in the preceding analysis would be practical considerationsin the lighter ftlie theoretical and mathematical analysis is to "be"interpreted and applied. Referring now Ztolfig 1 and considering for themoment angular displacements in the plane of the paper, let'us sup: posethat conditions .in the boiler areequalized, the water level standing atthe ll-ine E. frhe -manometric liqluid would stand at equal levels inthe 'U-tube -at -.the line e. We now ;Wish to impose the condition thatthe indications at ,the

U-tube will; not bealtered w-hen the system is inclined. Let :us assumethat the system is inclined so=thatthewater level takes the position -ofthe line E'. The water level in the chamber 5 at the centerwlin ethereof then stands ate-vertical :d-istance above the km E equal to Dsin -0, where D is the distance between the center line of the boilerand-the center line of the chamber -5 and a is the angle between E andE1, both as indicated ion the drawing, and -the difierence .be-

tween the heads impressed the two degs of the. manometer is D sin M810.B). where Sp, 3 :denotes the -:spe0lfic gravity -of"the boiler waterwhich isirlessiihan unity. w

Considering :no'w the-U --t1.1be we demand that the surtaces of themanometrio liquid therein remain at the linie e. The displacement givesrise to a head in the right-hand leg Lsequal to d sin flbS'gLFG) wheresp. G denotes the specific gravity of the manometri-c liquid, and :int'he left hand leg to a head: in the opposite sense equal to -11 sinelsp. W), whereSp. expresses the 'specific'igravity of the water at thealooation =of thermanometer which, being at a. different temperaturefrom the 'water pin the boiler, is 'di-fv ferent from Sp. B. For:equilibrium therefore,

Now, let us assume that :the water in boiler assumes the levelkindicatedby 'the dotted line 1-0 in .Fig. :1, giving rise to a differential headHtSp. B) therein. The level ofthe manometric liquid in thele'f-t-rhanddeg L will sink a distance R to the line 30 and in theright-hand .leg will rise to the line '20 tofpr oduce a compensating.head. As the columns-are balanced in the regions between the lines l0and 20 and in the regions below theline 30, the compensatinghead in themanometer thus 7 produced is equal to hlSp. G'- Sp. W), Hence I h 811.33 r H s G SpIW New, i'rwe assume the system to tilt so that the waterin the boiler new assumes thegpos'ition or the dotted line 40. the samerelation :must be maintained. 'CI'earlythis'will be true because bothnumerator 'and den'ominator ofthe' inst term or the above equation willmultiplied by K817... 'Wr-SQ. G), or, expressing it generically,

it I is the arithmetical difference between the "specifiegravi'ties ofthe manometric fluid and the'Wa'ter in the manometer whether the U-tubeis of :the-Ferect or the inverted type.

It will be noted that in the above analysis the 'cro'ss' se'ctionalareas of the legs L and L of the u tube do not appear. The indicationsof ;-the instrument. are read in the-leg l; and the cross .sectionsarechosen to give area ding, R, that is, a changeE-inlevel from a zeropoint having :a

definite desired ratio -(whichmay-be unity) to the -change in -level.-in the boiler which is measured, The reading R or variation from e intheleg L is equal to the f-raction 1 :1 (area "L") I I area L+afl a l/ HThes'e-,'a1feas do, not asset the ratio of H to n or the'trigohometricfunctions of the angle '0.1

"Ihereforefconsidering, as we have been doing,

theplane of thecenter line of theboiler-andfthe centen'lihe of .thechamber 5 to be 'the'same as the plane 'ofth center'l'lines of the'legsof ithe U -tdbe; surging due 'toinclina'tions of't'he systemcorresponding to rotations in that plane will be withoutefiect on themanometer. AyesseLfhowei7e"r,;may roll a'thwaftships, or .p'itch .foreand aft, or cihnbine'bbthlthesemotions. Further analysisis-vdiagram'rned in a ,g'e'neralized form in Fig. 2.

sfichm'o'tion may begcoiisideredas comprisi-n'gi'two 2 components "inrelatively vertical planes. L'e't draw. therefore, in a. horizontal.plane as shown in Fig. 2 :r ax'is through the center line 2 of the cup5 and a relatively perpendicular y a:iisthrough the center linef'C ofthe boiler '(not necessarily" athwarts'lilipsand'fore and aft planes)and Tletlus draw, parallel axes in and yfi through the legs I)"and'lrespectively o'f'ithe manometer.

Consiiiering movements infthe plane of "the .1! ends, the analysis whichhas beenpreviously given jinronnecti'onwith Fig. 1 applies and m: theplane pf the center line or the boiler and the center line orthe chamber5 on the one hand and the'plane dfthe'legsL and L" of the manometc:- areparallel, or they may coincide if the four points are coiinear. l

itshoald be noted that to have the 'inuic'atin '--sumc'e"in' indicatinglog L more in the direction as the liquid inthe container, the companionleg 15, which communicates with the water containing space of the boilerandmwhlich the variable pressure is exerted, 'shouldrbedisplaced'therefrom in the samesense (to the right viewing Fig. 1)that-thecupt is 'displacedrelatively to the center'line. l r

The verticalposition' of the determined by requirements of conveniencewithin wide limits andwill not affect the operation mutate-mam a wholeand its distance from ithe'i-boilerimay; be

In a given installation it wo'ul'd sordinarily be" convenient to fix thevalue of 1d and theniinstall the datum chamber 5 in accordance with the.

principles above explained.- This isfacilitate'd by placing thecupwithin theboiler as indicated in the diagram; Toplace such a cup withinthe boiler is not in itself new. but: ithas; not been suggested to place:it in accordance 'Withx'the' hydrostatic principles explainedfthelocation ap. parently havingbeenmade atlrandom'. i: In. thefdescriptionhitherto the. datumachjama her or cup has been referred .to .as.locatedat least as high as the normal high??:. .vvaterlevel installationis carried out, without too great in-' .improved indication which may bemost conveniently contrasted with the indicationwhich would begiven byyanormal-gageglass installed at the exterior .ofqthe boiler shell in thesame plane through the center line as the cup 5 so as to be affected inlike manner by either roll or pitch,

' :andetaking this as'aystandard of comparison, in

of the containeriand thecconnection therefrom is not only theconstantipressure connection but the high pressure connection. a In the,case of a boiler with overflowto thewate'r-containing spaces of theboiler .or in the case of a cup within the shell of the. container suchav location would ordinarily be the mostconvenient. The essential point,however, is to establish a fixed head conveniently near to the normaloperating levels in order to provide for a practicably smalldifferential pressure at the manometer independently of the actual headsthereon which might be very great on account of the relative positionsof the manometer and the container. This could be effected by a cup solocated, for example, as to predetermine a fixed head slightly below theusual low water mark or at or about approximate, but a certain-limit ofaccuracy in constructing a physical embodiment is assumed. Alsovariations even if beyond the reasonably possible accuracy of theoperations involved may give desirably useful results. In the presentinstance the specific gravity of the water in the boiler is, of course,taken from an assumed normal steam pressure. The specific gravities ofthe water at the manometer and of the manometric fluid vary inaccordance with the circumambient temperature. The determination of thecenter line of a large boiler drum would obviously not be accurate tovery small fractions of an inch. Assuming the correctness of the'centerline, it would probably be feasible to determine the distance D to anaccuracy of perhaps of an inch, amounting to an error of about 5%. Thecoincidence or parallelism of the plane of the center line and the cupwith the plane of the manometer legs can be quite accurately attained.We should not expect, however, in any instance that entire immobility ofthe indicating column at the manometer would be attained with the shipin a seaway, particularly since, as pointed out, the

water level may be affected by other factors, and useful results will beattained if the theoretical reierringto asubstantia'l reduction in thefiuc- =t1iationofthe indicating-surface I contemplate areduction to;anamount 25% or less of the fluctuation which would occurjn such a glass.

. I .I am aware. that the invention may be embodied :inother specificforms without departing from the spirit-1017., essential attributesthereof and I therefore desire thepresent embodiment to be consideredinall respects as illustrative andnot restrictive, as .is'in fact clearin several matters from'the descriptionitself. Reference is to be i hadto ,theappended claims to indicate those principles of, the inventionexemplified by the particular embodiment described and which I desire tosecure by LettersPatent.

1. In a liquid-level system for containers a manometer of the U-tubetype having spaced legs, one of which is constructed to' permit anobservation of the level of manometric liquid therein to be made, onebeing connected to the liquid-containing space of the container beneath'theoperating levels therein, and a cup to which the other leg isconnected, which cup is replenished with the liquid and has overflowmeans to establish therein a fixed head under the pressure of thecontainer, said cup being spaced from the vertical center line of thecontainer, the ratiosof the distances of the legs from relativelerpendicular reference planes passing therethrough to the distances ofthe center lines of the container and cup respectively from parallelreference planes passing therethrough being substantially equal to theratio between the specific weight of the liquid in the container to thearithmetical difference of the specific weights of the liquids in themanometer.

I 2. In a liquid-level system for containers a manometer of the U-tubetype having spaced legs, one of which is constructed to permit anobservation of the level of manometric liquid therein to be made, onebeing connected to the liquid-containing space of the container beneaththe operating levels therein, and a cup to which the other leg isconnected, which cup is replenished with the liquid and has overflowmeans to establish therein a fixed head under the pressure of thecontainer, said cup being spaced from the vertical center line of thecontainer, the legs of the U-tube being in a vertical planesubstantially parallel to or substantially coincident with the commonplane of the vertical center lines of the container and the cup, thespacing of the legs in their plane being proportioned to the spacing ofsaid center lines in accordance with the ratio of the specific Weight ofthe liquid in the cup to the arithmetical difference of the specificweights of the liquids in the manometer in such manner that surging ofliquid in the container and surging of the manometric liquid arecorrelated to tend toward compensation and provide an indication in themanometer wherein fluctuation of the in 4 diatiiig level issubstantially reduced es i cem pared with that Whih weuid e'c'cui' inanexteri or h mass nlieted t0 the boiler sheli i'n :the same i'eiativepbsiti'on to the eeriter line 'a'sthat e'ccilpi'ed by the *cup. 7

3-. In a liquid level indicating s ystem fbi cm?- ttinis a menemetei Ofthe U tube tyle having. spaced legs, one of which is Constructed topermit ah dbservati'oh of the l'evelof manom'etric iiqui'd therein to bemade, we leg being connectedto the iiquidwonteining space of'thecontainer bedeath the opeiatihg levels therein, and a cup to which theother leg is connected, which eub is plane being correlated so thaitthechanges of head in the Cup onth'e' one hand and-et'the mahometer on theother incident to equal an-gnlar displa'r'sements of the-parts in saidplanes substantiially compensate one another Within the limits of errorof the eppziiatus as a when.

4. In a liquid-level system for cohtaihers a manometer 6i thei-u tubetype having spaced legs; one ef whichis constructed to permit. ,anobservation (if the levelof manometric liquid therein to be made, onelegkbei'ng connectedto theliquid containihg space 'of the containerben'eath the operating levels therein, and a cup to. which the other legis'conne'ctei which eup is replenished with the liquid. and Has Overflowmeahs-to establish therein a fixed head under the pressure or theontainer, said cup being spaced fldm the vertieal center liiie of thecontainer, the distances of the legs from relatively perpendicularreference planes passing th'erethroug'h being propbrtibne'd to thedistances of the vertical center linebbf=the "uh and the acehtainerfrom'parallel reference planes passing therethrough in accord= ailcewith the ratio Dfthe spedifie weight; of the liquid in the cup to thearithmetical difieren'ce of the-specific' weights Ofrthe liquids in: themanemeter in suchm'anner that surging of. liquid the container andsurging of the menometri liquid are correlated to tend towardv"compens'zitien and provide an indication in the manometer whereinfluctuation of the indicating level i's'sub-

